The present invention relates to a device for controlling a diesel engine including injectors for injecting fuel into cylinders, and a turbocharger for compressing intake air by using exhaust energy.
Generally, diesel engines in which fuel is injected into cylinders which is increased in temperature and pressure by being compressed for self ignition excel in thermal efficiency compared to spark-ignition engines (e.g., gasoline engines), and have a lower discharge amount of CO2. Therefore, recently, such diesel engines have been widely familiarized not only as engines for large-sized vehicles (e.g., trucks), but also for passenger vehicles.
As control devices of such diesel engines, for example, JP1998-274088A discloses a control device that has been known. As disclosed in JP1998-274088A, in a diesel engine, an injection amount and an injection timing of fuel to be injected into a cylinder is determined based on an engine load and an engine speed, and the fuel injection amount is increased as the engine speed and the engine load become higher.
As described above, even though the fuel injection amount and the fuel injection timing are determined according to the engine load and speed, when the engine load is rapidly changed by, for example, a rough accelerator operation, there is a possibility that a maximum in-cylinder pressure determined by an amount of compressed air or an amount of heat of combustion inside the cylinder temporarily becomes excessively high. Especially, because the diesel engine in JP1998-274088A is provided with a turbocharger including a turbine driven by exhaust energy and a compressor for compressing intake air, a turbocharging amount may be excessively large due to a response delay of the turbocharger, and such phenomenon as described above (the excessive increase of the maximum in-cylinder pressure) easily occurs.